Grey Squirrels and Trees in Cumbria — The Damage They Cause and What Can Be Done

Grey squirrels are a familiar and widely enjoyed part of the wildlife of parks, gardens and woodland across Cumbria. They are also one of the most damaging invasive species in British woodland, responsible for a level of harm to native trees and birds that tends to be underappreciated by the public, possibly because squirrels are appealing to look at in a way that makes the scale of damage they cause difficult to reconcile with their presence.

In our work across South Lakeland, the Lake District and North Lancashire, grey squirrel bark stripping is one of the most common forms of tree damage we encounter. This article explains what it is, why squirrels do it, which trees are most affected and what the realistic options are for managing the problem.

What Bark Stripping Is and Why Squirrels Do It

Bark stripping by grey squirrels involves the removal of the outer and inner bark from the stems and branches of trees, typically during May and June when the bark is sappy and relatively easy to remove. The squirrels strip the bark to access the phloem, the sugary tissue immediately beneath, which at this time of year is particularly rich in energy and nutrients as the tree is in full active growth.

The behaviour appears to be socially transmitted, with young squirrels learning it from adults, and is most intense in years when other food sources are limited and the squirrel population is high. It is most prevalent in areas where squirrel densities are greatest, which in Cumbria tends to mean larger, more connected woodland blocks.

The damage caused by bark stripping is not cosmetic. When bark is removed from a significant proportion of a stem's circumference, the tree is unable to transport water and nutrients between the roots and the crown in that section. If the bark removal goes all the way around the stem, the tree dies above that point, because the flow of nutrients and water is completely severed. If the stripping covers less than the full circumference, the tree may survive but with a permanent wound that is an entry point for decay fungi and a long-term structural weakness.

Which Trees Are Most Affected in Cumbria

Grey squirrel bark stripping affects a wide range of species but is particularly severe on certain trees that are important components of the Cumbrian woodland landscape.

Beech is the species most severely affected. Beech bark is thin and smooth and strips very easily, and the phloem of beech is particularly rich in sugars during the growing season. Beech woodland in Cumbria, and young beech in mixed woodland and new woodland planting, is at serious risk of bark stripping damage in areas with high squirrel populations. In a severe year, a significant proportion of young to semi-mature beech can be killed outright by ring-barking.

Sycamore is also heavily affected and in some woodland management contexts this is regarded as a slightly lesser concern given that sycamore is a non-native species, but on commercial forestry sites where sycamore is being grown for timber, squirrel damage is a real economic problem.

Oak, ash, pine and various other species are also affected, though usually less severely than beech. Sweet chestnut, a species increasingly being considered for planting in Cumbria as climate change shifts the range of viable species northward, is also susceptible to significant squirrel damage.

The Impact on New Woodland Planting

This is the most practically significant aspect of the squirrel problem for anyone carrying out or planning woodland creation in Cumbria. New woodland planting that includes beech, or sycamore, in areas with significant squirrel populations can suffer devastating losses if squirrel control is not part of the management plan.

We always raise this with clients who are planning new woodland planting across our area. A significant investment in establishment, grant-aided or otherwise, can be largely undone by a single season of high squirrel activity in the seventh or eighth year after planting, when the trees are reaching the size most attractive to bark stripping. Planning for squirrel management from the outset, whether through trapping programmes, alternative species choices or specific monitoring, is important.

The Impact on Red Squirrels

It would be wrong to discuss grey squirrels and trees in Cumbria without mentioning red squirrels. Cumbria is one of the last strongholds for red squirrels in England, with significant populations in the woodlands of the north of the county including Kielder Forest and the northern Lake District. Grey squirrels are the primary reason that red squirrels have been eliminated from most of England: they out-compete red squirrels for food and habitat and carry the squirrelpox virus, which is lethal to red squirrels but does not affect grey squirrels.

The management of grey squirrel populations in Cumbria therefore has conservation implications that go beyond tree damage. Programmes like the Cumbria Red Squirrel Network and the work of local wildlife trusts involve active grey squirrel control specifically to protect the remaining red squirrel populations. The same management that benefits woodlands and trees in Cumbria directly supports the conservation of one of England's most endangered mammals.

What Can Be Done

Grey squirrel management is a genuinely difficult and emotive topic, and we want to be straightforward about what is and is not realistic.

Lethal control of grey squirrels through trapping is the most effective method of reducing squirrel populations in and around woodland. It requires sustained effort over multiple years, because squirrel populations recover rapidly when control ceases. It needs to be carried out by people who are licensed and trained to do so humanely and legally. It is most effective when coordinated across a landscape rather than on a single isolated site, because squirrels from surrounding areas will recolonise a cleared area quickly.

Tree guards and spiral wraps provide some protection for individual young trees in garden and small-scale planting contexts but are not practical or cost-effective at woodland scale.

Species choice can reduce risk but cannot eliminate it. Choosing species less attractive to bark stripping, such as oak, rowan, birch, alder and hazel rather than beech and sycamore, in areas with known high squirrel pressure reduces the likelihood of severe damage without eliminating the risk entirely.

For landowners considering new woodland planting in Cumbria, we recommend discussing the squirrel situation as part of the planning process. We are happy to give an honest assessment of the likely risk level on any given site.

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Email: enquiries@maxreynoldstreeservices.com

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